The present invention relates to a ski binding intended for disengageably attaching a boot to a ski, comprising a front binding, known as a stop, and a rear binding, known as a heel piece, this stop and this heel piece being held elastically in a determined position corresponding to the position of the boot attached to the ski, and in which position the front stop is held elastically by a spring arranged at least approximately longitudinally in the direction of the heel piece.
A binding of this kind is known from U.S. Pat. No. 5,735,541, the content of which is incorporated by reference. The longitudinally-mounted spring is a helical spring which opposes the pivoting of the jaw of the stop. The heel piece comprises an attachment body in which is mounted approximately vertically a spring which opposes the pivoting of a heel-gripping jaw which acts on the spring via a piston. The stop and the heel piece are connected by a bar which acts as a support for the heel piece, but they could be mounted on the ski independently of one another. Therefore, as far as the stop is concerned, this binding differs from previous ski bindings in which the release spring is mounted in the body of the stop. Moreover, this binding comprises, like the earlier bindings, a helical spring made of steel for each of the binding elements, front and rear. What is more, in the heel piece, the spring still occupies a significant volume of the body of the heel piece.
In document U.S. Pat. No. 5,899,484, the content of which is incorporated by reference, it has, incidentally, been proposed that, in one stop, the helical spring should be replaced by a blade working in buckling mode. A solution of this kind has the advantage that in buckling, the resistance offered by the blade drops sharply, allowing the boot to escape more easily, the buckled blade behaving like a spring of relatively low stiffness but with a high preload.
The present invention aims to produce a ski binding with a simpler stop, and heel piece, a small volume and allowing greater use of elements made of non-metallic composite.
To this end, the ski binding according to the invention is one wherein said spring, arranged at least approximately longitudinally, consists of at least one blade operating in buckling mode and also elastically retaining the stop.
This blade is arranged flat under the boot, in a space which becomes available by the raising of the boot, which is characteristic of the current tendency in favor of edge gripping. It is preferably made of a composite material such as fiber-reinforced plastic, the fibers being made of glass or of carbon or of KEVLAR (trade mark), but it could just as easily be made of metal.
The stop and the heel piece no longer have a spring. Forces can be applied from the jaws of the stop and of the heel piece to said blade simply using levers or cams.
The simplest construction consists in making the blade work in buckling mode between two parts that can move in longitudinal translation and are kinematically connected to the stop and to the heel piece, respectively.
The kinematic connections may be achieved using levers.
According to one embodiment of the invention, the stop and the heel piece are mounted on a longitudinal support in the form of a slide, in which there are mounted two sliders associated respectively with the stop and with the heel piece so as to be carried along toward one another when the stop or the heel piece is displaced relative to its position of rest, said blade being mounted between these two sliders.
With the exception of the levers which provide the kinematic connection between, on the one hand, the stop and the heel piece and, on the other hand, the sliders, the stop and the heel piece may be made in the known way and it is even possible to re-use the existing stop and heel piece elements in their current form. As far as the heel piece is concerned, the piston found in many heel pieces is advantageously kept as an intermediate element between the jaw and the lever, for applying the force of the jaw to the lever, this piston advantageously being guided in a direction that encourages forces to be transmitted from the jaw to its slider.
The setting of the binding may be adjusted simply by using a part surrounding the blade and mounted like a nut on a longitudinal adjusting screw mounted and retained axially in one of the sliders.
It should be remembered that in order to adjust the length of the binding, that is to say to alter it to suit the size of the boot, it is necessary for it to be possible to move the heel piece relative to its slider, and this means that it must be possible for the point connecting the heel piece to its slider to move. To adjust the length, the heel piece will generally be in such a position that the blade has moved beyond its buckling point and it is necessary to keep the blade in that condition during adjustment. This can be done simply using an auxiliary screw stop screwed longitudinally into said longitudinal support.